Dirac Medallists 1991

Stanley Mandelstam (L) and Jeffrey Goldstone

Stanley Mandelstam, University of California,
Berkeley, USA

in recognition of his contributions to the development of
theoretical physics. His representation of the analytic properties
of scattering amplitudes in the form of double dispersion relations
(Mandelstam representation) is basic to the modern understanding of
relativistic particle scattering and his seminal work on the
quantization of string theories, exploiting their conformal
properties, led to a more profound understanding of this subject.
Mandelstam was among the first to apply path integral quantization
methods to string theory. This work was generalized and extended by
many others in the following years and now forms an integral part
of the modern formulations.

for his fundamental clarification of the phenomenon of
spontaneous symmetry violation in relativistic quantum field
theory. This phenomenon has come to occupy a central role in our
understanding of elementary particles, and Goldstone's work is now
among the foundations of the standard model of fundamental
interactions. The ensuing massless bosons, known as Goldstone
bosons, have found crucial applications also in many spontaneous
symmetry breaking processes in condensed matter physics.